I'd never have guessed. In British English, if slightly dated (the first example that came to mind was 'It's high time you learnt some manners' - typical of teachers of a certain vintage), it's perfectly urban.
I might have guessed it was an abbreviation for "rural" but I would have disagreed with it. It's certainly a common enough phrase in BrE, in all parts of the country.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.